Organic photoconductor-(mononitro-2-aza-fluorenylidene)malononitrile charge transfer complex

ABSTRACT

Photosensitive material for use in electrophotography which is a charge transfer complex comprising (mononitro-2-aza-9fluorenylidene) malononitrile and an organic photoconductor.

ite J Hashimoto 1 Feb. 18, 1975 [54] ORGANIIC 3,484,237 12/1969 Shattucke461 96/15 PHOTOCONDUCT0R (M0N0NITR0 2 3,485,625 12/1969 Fox..... 96/153,556,785 1/1971 Baltazz|.'...,..,.. 96/15 x 3,583,869 6/1971 T b k 1 1.96 1.5

FLUORENYLIDENE)MALONONITRILE 3,595,648 7/1971 96/15 x CHARGE TRANSFERCOMPLEX 3,674,473 7 1972 BlaflCl'lEItfi 96/15 3,677,752 7 1972 L k -1.96 1.5 x

[75] Inventor Hashlmmo Tokyo Japan 3,752,668 8/1973 96/15 [73] Assignee:Kabushiki Kaisha Ricoh, Tokyo,

Japan [22] Filed: Jan. 24, 1973 [21] Appl. N0.: 326,563

[30] Foreign Application Priority Data Jan. 24, I972 Japan 479293 [52]US. Cl 96/l.5, 96/].6, 260/294.9, 260/297 R, 260/297 T, 252/501 [51]lint. Cl G03g 5/00 [58] Field Of Search 96/15, 1.6; 252/501 [56]References Cited UNITED STATES PATENTS 2,980,535 4/1961 Schroeter 96/1.5X 3,244,516 4/1966 Neugebauer et a1 96/1.5 3,252,794 5/1966 Schaum eta1. 96/1.5 3,301,676 I/l967 Tomanek v 1 1 96/15 3,307,940 3/1967 Haeglet a1 1. 96/l.5'

3,796,572 3/1974 Hashimoto 96/15 OTHER PUBLICATIONS Wagner et al., AStudy of the Relation of Electron Affinity to the Photoconductivity ofDoped Poly-N- Vinylcarbazale Films: A New Method of Analyzing thePhotoresponse, Photographic Science and Engineering, Vol. 14, No. 3,MayJune, 1970, pp. 205209.

Primary Examiner-Morman G. Torchin Assistant ExaminerJohn R. MillerAttorney, Agent, or FirmCooper, Dunham, Clark, Griffin & Moran [57]ABSTRACT Photosensitive material for use in electrophotography which isa charge transfer complex comprising (mononitro-2-aza-9-fluoreny1idene)malononitrile and an organic photoconductor.

1 Claim, 1 Drawing Figure 5, g H ETHEIZ CH3 Hun -11,90 11/ BACKGROUND OFTHE INVENTION A. Field of the Invention The present invention relates tonovel compositions suitable for use in electrophotography.

B. Description of the Prior Art Electrophotography is an art whichusefully combines photoconductivity with electrostatic phenomena. A widevariety of inorganic substances as selenium, zinc oride, and the likehave heretofore been employed as photoconductors. Recently, however,organic photoconductive substances such as poly-N-vinyl carbazole andothers have attracted wide attention. They are of particular interestbecause of their advantageous properties with respect to cost ofproduction, transparency of product film, ease of film forming, etc.Despite these advantages, their wide adoption has been impeded becausethey are generally inferior to inorganic substances in sensitivity andexhibit only marginal sensitivities in the visible region of thespectra. This problem has been somewhat alleviated by the use of varioussensitizing substances. Another problem which has retarded the adoptionof organic photoconductors is that it is difficult to preserve them.

SUMMARY OF THE INVENTION One object of the present invention is toprovide organic photoconductive compositions which manifest usefulsensitivity in the visible region of the spectrum.

Another object of the present invention is to provide organicphotoconductive compositions which are superior in film transparency,film formability, preservability, etc. A principal feature of theinvention is the provision of a charge transfer complex comprising anovel (mononitro-Z-aza- 9-fluorenylidene) malononitrile electronacceptor and any known organic photoconductive electron donor. 1

DETAILED DESCRIPTION OF THE INVENTION The above mentioned chargetransfer complex comprising (mononitro-Z-aza-9-fluorenylidene)malononitrile as the acceptor and various organic, photoconductivedonors comprise the photoconductive compositions of the presentinvention. The compositions display panchromatic sensitivity and areuseful with actinic light in the visible region of the spectrum. Theirutility can be enhanced however by the addition of known sensitizerssuch as Rhodamine B, Rose Bengal, fluorescein and the like.

Preparation of electrophotographic compositions of the present inventioncan be easily effected by: mixing (mononitro-2-aza-9-fluorenylidene)malononitrile, the acceptor, with the selected donor in the weight ratioof from 1:100 to 1501100; adding such additives as may be desired suchas binders, additional sensitizers and other conventional additives tothe resulting mixture; dissolving the mixture in an appropriate inert,organic solvent such as dioxane, tetrahydrofuran, etc.; subsequentlycoating the thus obtained solution on an appropriate substrate. Suitablebinders include, for example, novolak, acrylic resins and others of thetype conventionally employed. Suitable substrates include, for example,aluminum plates, polyester films with a vacuum deposited aluminum layer,paper treated for conductivity, etc. The final product is dried.

Typically, a composition of the invention may contain added binder inthe range of about 5 to 50 parts by weight relative to the total weightof the mixture, and additional sensitizers such as fluorescein in theweight range of about 0.001 to 0.0] parts by weight based on the weightof the donor.

Typical donors which may be employed in this invention includecondensation polycyclic compounds such as pyrene, perylene, anthracene,etc., phenothiazine,

phenoxazine, thionine, 9,9-diphenyl-9,10- dihydroanthracene,2,3-diphenyl pyrrocoline, a,w-bis( N-carbazolyl )-propane, N ,N,N,N-tetrabenzyl-P-phenylene diamine, 1,6-dimethoxyphenazine,1,8-bis(dimethylamino)-naphthalene, 1,1,5-triphenylbrom-1-en-4-in-3-ol,N-ethyl carbazole, N- propyl carbazole,3,6-dibrom-N-ethyl carbazole, 2- phenyl-3-P-dimethylaminophenylquinoxaline, acridine, p,p-bis-dimethylamino biphenyl, p,p'-bisdiphenylamino biphenyl, 2,3,4,5-tetrakis (p-dimethylaminophenyl)-pyrrole, 2-p-diimethylaminophenyl- 3,4-diphenyl imidazole,2,5-lbis(p-dimethylaminophenyl)-l,3,4-oxadiazole,4-phenyl-5-pdimethylaminophenyl-3H-2-imidazolone, etc., and, ashigh-molecular compounds, there may be poly-N-vinyl carbazole,poly-3-vinyl-N-ethyl carbazole, polyphenylene pyrazole,poly-l-allyl-4,5-diphenyl imidazole, polyvinyl pyrene, polyvinylphertanthrene, polyacenaphthylene, poly-N-vinyl-3,6-dibromocarbazole,polyvinyl dibenzothiophene, poly-9-vinyl acridine, poly-N- allylphenothiazine, poly-P-imidazolyl-(Z)-styrene, polyvinyl anthracene,poly-P-phenylene-l,3,-oxadiazole, anthracene-formalin condensationresin, polypylomeritimide, vinyl anthracene-N-vinyl carbazole copolymer,l,2dihydroacenaphthene-indene copolymer, pyrene-formalin condensate,polyvinyl Malachite Green, polyvinyl dibenzofuran, poly-Z-vinylquinoline, poly-Z-vinyl furan, poly-3-benzofuran,poly-2-vinyl-4-(4'-dimethyl aminophenyl)-3-phenyl oxazole, as well asreaction products between polyvinyl amine and anthracene-9-aldehyde,naphthaleneformalin resins, N-ethyl carbazole-formalin resins, etc.

The (mononitro-2aza-9-fluorenylidene) malononitrile for use in thepresent invention can be synthesized by the following procedure:

First, by effecting Friedel Krafts reaction between hydrochloridenicotinic acid chloride and mesitylene in accordance with Reynold C.Fuson and John J. Millers method [cf.J.Am.Chem. Soc. 79.3477 (1957)],3-mesitol pyridine (yield: 63 percent, b.p.:l57.5158 C/4mml-Ig) isobtained.

Next, by phenylizing this reaction product through Grignard's reaction,3-mesitol-4-phenyldihydropyridine (yield: 76 percent, m.p.:l83l85.5 C;light yellow powder) is obtained. Further, by oxidizing this productwith chloranil in benzene, 3mesitol-4- phenyl pyridine is obtained.

When the thus obtained compound is subjected to ring formation byutilizing polyphosphoric acid, there is obtained 2-aza-9-fluorenone toserve as the material. Then by reacting this material with mixedsulfuric and nitric acids in an acetic acid solvent at a temperature ofabout C for lhour, mononitro-2-aza-9- fluorenone which is principallythe 7-nitrated product is obtained.

Subsequently, by making this mononitro-Z-aza- 9fluorenone react withmalononitrile in methanol in the presence of piperidine as catalyst, theintended (mononitro-2-aza-9-fluoreny1idene) malononitrile is obtained.The reactions are shown in FIG. 1.

The photosensitive compositions of this invention comprising a chargetransfer complex containing (mononitro-2-aza-9-fluorenylidene)malononitrile and an organic photoconductive donor as the principalcomponents are sensitive in the visible region of the spectrum, havesatisfactory preservability and reproducibility, and. are furtherapplicable to the transfer process. When deposited on an electricallyconductive substrate they form excellent electrophotographic plates.

The following non-limiting examples are given by way of illustrationonly:

EXAMPLE 1 A solution obtained by dissolving 64 mg of poly-N- vinylcarbazole, 91 mg of (7-nitro-2-aza-9- fluorenylidene) malononitrile and100mg of diphenyl chloride in 10 g of tetrahydrofuran is coated by meansofa doctor blade having wet gaps of 200p, on an aluminum coated Mylarfilm and dried to produce an electrophotographic plate having aphotosensitive film layer about 10 microns thick.

Subsequently, the thus prepared plate is charged by means of coronadischarge (-6KV), exposed to light by means of an apparatus equippedwith a tungsten lamp capable of producing an intensity ofillumination onthe sensitive surface of the plate of 3 luxes and measured for itssurface potential, whereby the time required for decreasing saidpotential to half (hereinafter referred to as exposure time required forhalf decay) is measured. It was found that the exposure time requiredfor half decay is about 4 seconds.

Similar results are obtained with poly-N-vinyl-3,6- dibromocarbazole andpoly-N-vinyl-3 chlorocarbazole.

EXAMPLE 2 A solution is prepared by dissolving 900 mg of poly-N-viny1-3-bromocarbazole, 91 mg of (7-nitro-2-aza-9- fluorenylidene)malononitrile and mg of diphenyl chloride in 15 g of tetrahydrofuran.When this composition is treated in the same manner as the compositionsof Example 1 it is found that the exposure time required for half decayis about 3.5 seconds.

EXAMPLE 3 A sensitive material is prepared in the same way as in Example1 except for increasing the amount of (7- nitro-2-aza-9-fluorenylidene)malononitrile to 910 mg from 91 mg as employed in Example 1. Theexposure time required for half decay of this sensitive material isabout 1.5 seconds.

EXAMPLE 4 A sensitive material is prepared in the same way as in Example2 except for increasing the amount of (7- nitro-2-aza-9-fluorenylidene)malononitrile to 910 mg from 91 mg as employed in Example l.The exposuretime required for half decay of this sensitive material is about 1.4seconds.

EXAMPLE 5 fluorenylidene) malononitrile.

1. A PHOTOSENSITIVE MATERIAL FOR USE IN ELECTROPHOTOGRAPHY WHICH IS ACHARGE TRANSFER COMPLEX COMPRISING 100 PARTS BY WEIGHT OF AN ORGANICPHOTOCONDUCTOR AND 1 TO 150 PARTS BY WEIGHT OF(MONONITRO-2-AZA-9-FLUORENYLIDENE) MALONONITRILE.